Use PHP to verify that the email is correct

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Reprint please indicate the source

When you register on a forum, there is usually an e-mail address verification function, when you enter an illegal format, there will be some kind of error message.

We can use the following rule expression
Ereg ("^[a-za-z0-9_]+@[a-za-z0-9\-]+\.[ A-za-z0-9\-\.] +$] ", $email);

But the function of the above equation is to check only strings and not output. We can further use this formula to achieve the function of returning information:
if (eregi ("^[a-za-z0-9_]+@[a-za-z0-9\-]+\.[ A-za-z0-9\-\.] +$] ", $email)
{
return FALSE;
}

Here we can go further to detect the host name, does it exist:
List ($username, $domain) = Split ("@", $email);
if (GETMXRR ($domain, $mxhost))
{
return TRUE;
}
Else
{
if (Fsockopen ($domain, $errno, $errstr, 30))
{
return TRUE;
}
Else
{
return FALSE;
}
}

Now we'll organize the top two features in PHP to form a function:
function Checkemail ($email)

{if (eregi ("^[a-za-z0-9_]+@[a-za-z0-9\-]+\.[ A-za-z0-9\-\.] +$] ", $email)
{
return FALSE;
}

List ($username, $domain) = Split ("@", $email);

if (GETMXRR ($domain, $mxhost))
{
return TRUE;
}
Else
{
if (Fsockopen ($domain, $errno, $errstr, 30))
{
return TRUE;
}
Else
{
return FALSE;
}
}
}

We can then use this function to detect the existence of an incoming email, for example:

if (Checkemail (web@webjx.com) = = FALSE)
{
echo "The E_Mail you entered is not correct.";
}
Else
{
echo "The input e_mail is correct."
}